1. Field of the Invention
The present invention generally relates to a vehicular engine. More particularly, the present invention relates to an engine controller for performing ignition timings and similar controls.
2. Description of the Related Art
The Japanese Unexamined Patent Publication 1-195951 discloses a conventional engine control device, which controls the ignition timings and fuel injections. In this conventional control device, the characteristics of the ignition timing control and the fuel injection control, while the engine is idling, differ from those during the engine non-idling operation. This control device determines whether the engine is in the idling condition, based on a signal transmitted from a throttle sensor. The throttle sensor is disposed along an intake passage, for detecting the opening angle of the throttle valve. The throttle sensor outputs the signal indicative of the opening angle amount of the throttle valve, and an idling signal reflective of the state of an idling contact switch, which generates an idling signal. The idling contact switch is ON when the throttle valve fully closes the intake passage, otherwise this switch is OFF.
The ignition timing of this control device is set in the more advance angle side, for reflecting the high output power of the engine, during the non-idling state or condition. When the engine is in the idling condition, the ignition timing is set in the more delay angle side, reflecting stability of the idling condition. When the engine speed exceeds a predetermined value during the idling state, fuel supply to the engine is interrupted.
The control device determines that the engine is in the idling condition, after a delay period has elapsed from the time the idling signal has switched from the OFF state to the ON state. The reasons for the delay period, on detecting the idling condition, are to delay (1) the ignition timing, and (2) the fuel supply interrupting more than when the throttle valve fully closes the intake passage. As a result, its delaying moderates the changes in the engine torque and air-fuel ratio. Such control prevents reductions of drivability because of torque shock, and of the exhaust emission resulting from a change of the air-fuel ratio.
Furthermore, in this conventional device, the delay period for determining the idling condition, in relation to the ignition timing control, is relatively shorter than the corresponding delay period related to the fuel injection control. Setting this delay period compensates for the difference between the actual air intake volume when the throttle valve fully closes the intake passage, and the apparent air intake volume, so as to prevent the ignition timing from being controlled in excessive advance angle.
However, when the engine is not actuated for some time, most of the lubrication oil, which is usually supplied to every part of the engine, generally drops into an oil pan. Consequently, the oil would not lubricate every part of the engine. As a result, the pistons and connecting rods might generate tapping noise, because of the lack of lubricating oil. Noise tends to occur more often, and becomes louder, as the combustion pressure increases, in other words, as the engine torque becomes larger. Therefore, one drawback of the conventional control device is the generation of noise when the engine is operational, since the detection of the idling condition is delayed.
The following illustrative example is given for further classification of the foregoing drawback. If an engine were provided with a throttle opener for preventing the fully closed throttle valve from adhering to a bore wall of the intake passage, when the engine is not actuated, the throttle opener keeps the throttle valve at a slightly opened (or shifted) position, in comparison with the fully closed position. Further when the engine is actuated, the throttles opener causes the throttle valve to switch to the fully closed position from the slightly opened position, under negative pressure.
Consequently, the throttle sensor causes the idling signal to switch from the OFF state to the ON state, simultaneously with the engine activation. Thereafter, the control device determines that the engine is in the idling condition, when a predetermined delay period has elapsed, subsequent to the switching of the idling signal to the ON stage.
Therefore, the ignition timing is to be advanced by the duration length of the delay period, and thereafter delaying. While the ignition timing is advanced by the delay period, the engine torque continuously increases. Therefore, if lubricating oil is not adequately supplied while the engine is actuated, loud noise is generated.
To resolve such problems, two attempted solutions were proposed. The first proposed solution is to use the ignition timing, which is set in the delay angle side specially for idling, regardless of the idling signals, even while the engine is operating. However, some drivers tend to operate the engine with the throttle valve open. Thus, this first solution would not solve the foregoing problems completely. The second proposed solution is to shorten the delay period uniformly at the idling determination time. However, this adversely affect the drivability and the exhaust emission, during the engine running.